JP4865281B2 - Method for producing active material for non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to a novel method for producing an active material for a non-aqueous electrolyte battery.

  A typical example of the non-aqueous electrolyte secondary battery is a lithium ion secondary battery. Lithium ion secondary batteries have high energy density and can be reduced in size and weight. A lithium ion secondary battery generally has the following structure.

In other words, a lithium ion secondary battery has a positive electrode plate in which an active material is applied to a current collector and a negative electrode plate in which an active material is applied to a current collector in a spiral shape through a separator serving as an insulating film. And the electrode plate group is enclosed in an exterior together with a non-aqueous electrolyte.
As the separator, for example, a microporous film made of polyethylene resin or polypropylene resin, or a polymer film made of polyethylene oxide, polyvinylidene fluoride, or polyacrylate is used as one that is insoluble in the nonaqueous electrolyte.

Nonaqueous electrolytes include polymer gel electrolytes and nonaqueous electrolytes. The polymer gel electrolyte is a polymer electrolyte containing a non-aqueous electrolyte. In the non-aqueous electrolyte, a solute composed of a lithium salt is dissolved in a non-aqueous solvent. Examples of the solute include lithium hexafluorophosphate (LiPF ₆ ), and examples of the nonaqueous solvent include ethylene carbonate and dimethyl carbonate.
As the positive electrode active material, a lithium-containing transition metal oxide such as lithium cobaltate (LiCoO ₂ ) is used. For the negative electrode active material, for example, a carbon material such as graphite is used as a material capable of inserting and extracting lithium ions.

  As the positive electrode active material, various materials have been studied in the past, but in the market, lithium cobaltate or a material obtained by substituting a part of cobalt of the lithium cobaltate with another element is used. These materials release oxygen at a high temperature, particularly in a charged state from which Li is removed, and this release of oxygen can oxidize the nonaqueous electrolyte, causing the battery temperature to rise abnormally, resulting in ignition and rupture. Usually, various control functions are provided in the lithium ion secondary battery so that such an abnormal temperature rise does not occur.

In recent years, a compound having an olivine structure (LiFePO ₄ ) has attracted attention as a safe positive electrode active material that does not release oxygen at high temperatures. Further, as a positive electrode active material having a higher capacity, a positive electrode active material such as Li ₂ CoPO ₄ F has also been proposed (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-229126

Formula containing _{Li 2 CoPO 4 F: Li 2} MePO 4 F ( where, Me is at least one element comprises at least a divalent transition metal) are those having a structure that is different from the olivine structure such as LiMePO ₄ In addition, since 2 moles of lithium per mole of the active material is included, there is a possibility that a maximum of 2 moles of lithium can contribute to charge and discharge, and a high energy density can be expected.

However, Patent Document 1 adopts a method of manufacturing a positive electrode active material by putting a raw material of a desired positive electrode active material in a platinum tube, vacuum-sealing the platinum tube with a quartz tube, and firing at 780 ° C. for 24 hours. In particular, this method makes it difficult to synthesize Li ₂ MePO ₄ F using Fe or Mn at the Me site, and characteristics such as charge / discharge capacity are insufficient when the positive electrode active material is applied to a battery. There was a problem of being.

Therefore, the present invention solves the conventional problems as described above, and particularly an active material made of a material containing Li ₂ MePO ₄ F that can exhibit characteristics such as sufficient charge / discharge capacity when applied to a battery, An object of the present invention is to provide a method for producing a positive electrode active material that can be easily produced even when Fe or Mn is used in the site of Me.

In order to solve the above problems, the present invention provides:
A mixture obtained by mixing raw materials of a material represented by the formula: Li ₂ MePO ₄ F (wherein Me is at least one transition metal element selected from the group consisting of Fe, Co, Mn and Ni) A method for producing an active material for a non-aqueous electrolyte battery, comprising obtaining a non-aqueous electrolyte active material containing a material represented by the above formula by melting

Here, in the above manufacturing method, it melted by allowing the mixture to warm at 1000 ° C. / h or higher.
Further, the material represented by the formula obtained by the present invention: Li2MePO4F (wherein Me is at least one transition metal element selected from the group consisting of Fe, Co, Mn and Ni) is amorphous. Is preferred.

According to the manufacturing method of the present invention as described above, an active material containing Li ₂ MePO ₄ F capable of exhibiting characteristics such as sufficient charge / discharge capacity when applied to a battery, particularly Fe or Mn in the Me site. Even if it is a case, it can manufacture easily.
According to the present invention, for example, Li ₂ CoPO ₄ F and Li ₂ NiPO ₄ F, as well as materials represented by Li ₂ FePO ₄ F and Li ₂ MnPO ₄ F, which are difficult to synthesize due to low reactivity of the raw materials, are also available. It can be easily manufactured in a short time.

The present invention relates to a nonaqueous electrolyte battery comprising a material represented by the formula: Li ₂ MePO ₄ F (wherein Me is at least one transition metal element selected from the group consisting of Fe, Co, Mn and Ni). The present invention relates to a method for producing an active material, comprising the steps of mixing raw materials of the materials and melting the obtained mixture to make it into a molten state once.

Thus, once in a molten state, the raw material reacts much more uniformly than a normal solid phase reaction, and a synthesis reaction of Li ₂ MePO ₄ F, which is a target substance, easily occurs. Further, in the conventional method, as much as 24 hours are required for the firing time, but according to the present invention, it is possible to manufacture in a short time by including a step of once melting.

  In a preferred embodiment of the present invention, the temperature at which the raw material mixture is melted is not a problem as long as it is equal to or higher than the melting point of all raw materials, but depending on the combination of raw materials, the mixture melts at a temperature lower than the melting point of each raw material. There may be cases. In short, it is only necessary to melt, and if it is melted, there is no problem even if it is below the melting point of each raw material. However, it is preferable to melt at a temperature equal to or higher than the melting point of all raw materials as a guide for reliably melting.

  There is no particular limitation on the method for cooling the molten mixture once the raw material mixture has been melted. For example, either rapid cooling or slow cooling (including natural cooling) can be used. Can be manufactured.

  For example, in the case of rapid cooling, a completely amorphous material can be produced depending on conditions. The material in the amorphous state is considered to be an aggregate of microcrystals, but it is a collection of very fine crystals. Therefore, when a battery is assembled as a positive electrode active material, excellent rate characteristics are obtained. There is an effect that can be obtained.

On the other hand, in the case of slow cooling, although depending on the cooling temperature, a material in a crystalline state or a mixed state of a crystalline state and an amorphous state can be produced. In particular, it is possible to obtain crystalline Li ₂ FePO ₄ F, which is difficult to manufacture by the conventional method.

However, since the composition ratio of the material in the mixed state of the amorphous state and the crystalline state as described above varies depending on the type of Me in Li ₂ MePO ₄ F, the amorphous state, the crystalline state, or the crystalline state Although it is difficult to uniformly distinguish between the mixed state of the state and the amorphous state, those skilled in the art can control to some extent by appropriately changing the cooling rate and the like.

  Various methods are conceivable as specific methods for cooling the molten mixture. The above molten mixture may be rapidly or gradually cooled by a furnace temperature program, etc., and the molten mixture may be taken out from the furnace and rapidly cooled or gradually cooled, or dropped into liquid nitrogen or the like. . Alternatively, the molten mixture may be cooled by extruding it with argon gas or the like and applying it to a rotating copper roller using a melt quenching device or the like. In this case, the cooling rate can be changed depending on the number of rotations of the copper roller.

It is more preferable that the heating rate in the step of bringing the raw material mixture into a molten state is faster. When the molten mixture obtained by rapidly melting the raw material mixture is cooled, a material having a large capacity (particularly Li ₂ FePO ₄ F) having a crystalline state or a mixed state of a crystalline state and an amorphous state is obtained. Can be manufactured.

Heating rate in the step of rapidly heated, the Ru der 1000 ° C. / h or higher. By doing so, the side reaction in the raw material mixture at a low temperature can be suppressed, and the reaction and synthesis for realizing a desired composition can be more easily caused.

  Various apparatuses can be used as an apparatus used for increasing the melting temperature at 1000 ° C./h or more. For example, a device having an induction heating method using a coil, a device that rapidly raises the temperature by infrared irradiation, and a device that rapidly raises the temperature of the heating element by causing a current to flow rapidly. Alternatively, a method of rapidly raising the temperature by directly putting the raw material mixture in a furnace set at a preset temperature can be used.

The starting material in the method for producing a nonaqueous electrolyte battery material of the present invention, that is, the formula: Li ₂ MePO ₄ F (wherein Me is at least one transition metal selected from the group consisting of Fe, Co, Mn and Ni) There are roughly two types of methods for selecting the raw material of the material represented by (element).

The first is LiMePO ₄ having a previously synthesized olivine structure (Me is at least one transition metal element selected from the group consisting of Fe, Co, Mn, and Ni) and a fluoride of LiF or Me (for example, In this method, a combination with a fluorine compound such as CoF ₂ , CoF ₃ , FeF ₂ , FeF ₃ , MnF ₂ , MnF ₃ , NiF ₂ , NiF ₃ ) is used as a raw material.
In this case, there is an advantage that a side reaction hardly occurs, but in some cases, it is complicated in that the synthesis needs to be performed in two stages.

  The second is a method using a combination of raw materials used to make a compound having an olivine structure. Specifically, a lithium source, a Me source, and a phosphorus source are required. As the lithium source, for example, various lithium salts such as lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxide, and lithium fluoride lithium phosphate can be used.

As the Me source, for example, oxalate, acetate, carbonate, hydroxide, nitrate, oxide and phosphate can be used, and further, Me element powder itself can be used as a fuel. it can. As the phosphorus source, for example, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphorous pentoxide, lithium phosphate, and Me phosphate can be used.
In this case, side reactions are likely to occur, but there is an advantage that the synthesis can be performed in one step.

The active material produced by using the method for producing an active material for a nonaqueous electrolyte battery of the present invention can be suitably used as a positive electrode active material for a nonaqueous electrolyte battery (for example, a lithium battery).
The lithium battery includes a positive electrode, a negative electrode, an insulating layer that separates them, and an electrolyte. The electrolyte is a medium that moves ions, and a nonaqueous electrolytic solution (including a gel polymer electrolyte) or a lithium ion conductive solid electrolyte can be used.

When a non-aqueous electrolyte is used as the electrolyte, a solute that becomes a supporting electrolyte salt is dissolved in a non-aqueous solvent.
As the solute, at least one kind of commonly used alkali metal salts may be used. For example, fluorine-containing inorganic anion salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , NaPF ₆ , and NaBF ₄ , and LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN Lithium imide salts such as (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) and LiN (CF ₃ SO ₂ ) ₂ are preferred.

  Examples of the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate and vinylene carbonate, acyclic carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, γ-valerolactone and δ. Lactones and derivatives thereof such as valerolactone, furans and derivatives thereof such as tetrahydrofuran and 2-methyltetrahydrofuran, ethers and derivatives thereof such as 1,2-dimethoxyethane and 1,2-diethoxyethane, diglyme, triglyme and Glyme such as tetraglyme and its derivatives, amides such as N, N-dimethylformamide and N-methylpyrrolidinone, ethylene glycol And alcohols such as propylene glycol, methyl acetate, ethyl acetate, esters such as methyl propionate and ethyl propionate, phosphoric acid or phosphoric acid esters, dimethyl sulfoxide, sulfolane and its derivatives, such as dioxolane and derivatives thereof.

The non-aqueous electrolyte solution preferably contains at least one of these non-aqueous solvents. Furthermore, you may add the additive generally used to the said non-aqueous electrolyte.
When a solid electrolyte is used as the electrolyte, a lithium ion conductive inorganic solid electrolyte or a lithium ion conductive solid polymer electrolyte may be contained in the insulating layer in the positive electrode, the negative electrode, or the like. In this case, since it does not contain an organic electrolyte, there is no worry of leakage and it is safer.

  Although the material which comprises the separator used as an insulating layer is not specifically limited, For example, polyethylene, a polypropylene, a polyimide, a polyethylene oxide, a polyvinylidene fluoride, a polyacrylate etc. are mentioned. Further, a filler may be added to improve the mechanical strength.

  Specific examples of the separator include, for example, a microporous film made of polyethylene or polypropylene, a porous film containing polyimide to improve heat resistance, or a film containing fine particles of alumina, silica, and titania. Those with improved mechanical strength are used.

  In the present invention, a polymer polymer that contains and holds an electrolytic solution in the insulating layer may be used, and a so-called polymer gel electrolyte may be used. There is also a method of obtaining a gel polymer electrolyte by further mixing the monomer solution and various non-aqueous electrolytes and polymerizing them, including the separator. These gel polymer types have a feature that there is no worry of leakage.

The negative electrode active material is not particularly limited. For example, (1) a material that can be used as a host material for lithium ions that are alkali metal ions, such as amorphous carbon materials, carbon materials such as artificial graphite and natural graphite, and the like (2) Metals such as aluminum (Al), lead (Pb), tin (Sn), bismuth (Bi) and silicon (Si), and alloys of these with other elements, lead (Pb), tin (Sn), bismuth (Bi) And silicon (Si) oxides, alkali metal interstitial interstitial intermetallic compounds (AlSb, Mg ₂ Si and NiSi ₂ ), lithium nitrogen compounds (general formula Li _(3-X) M _X N ( Here, M represents a transition metal)), a titanium spinel compound (Li ₄ Ti ₅ O ₁₂ ), a lithium vanadium oxide, or a material that can be alloyed with an alkali metal ion is preferable.

Hereinafter, the Example of the manufacturing method of the positive electrode active material of this invention is described.
Example 1
LiFePO ₄ and LiF were used as raw materials. LiFePO ₄ can be produced using known techniques. Here, it synthesize | combined with the following method.
Lithium carbonate, iron oxalate dihydrate, and ammonium dihydrogen phosphate were mixed at a predetermined ratio, and the mixture was calcined in an argon stream at 300 ° C. for 12 hours. The obtained calcined product was pulverized and mixed again, and then calcined at 600 ° C. for 24 hours in an argon stream to obtain a powder. As a result of X-ray diffraction measurement, it was confirmed that the obtained powder was LiFePO ₄ having an olivine structure.

This LiFePO ₄ powder and LiF powder were mixed well at a molar ratio of 1: 1 to obtain a raw material mixture. This raw material mixture was heated and melted using a high-frequency induction heating system for coils.
First, the raw material mixture was placed in a platinum tube having an inner diameter of 5 mm and a through hole having a diameter of 0.3 mm at the tip, and this tube was placed in a quartz tube having an inner diameter of 7 mm. This quartz tube was set in an induction coil of a liquid quenching apparatus (RQM-T-50 manufactured by Makabe Giken Co., Ltd.). Next, high frequency power was applied to the induction coil, and the platinum tube was gradually heated. Heat is transferred from the heated platinum tube to the raw material mixture of LiFePO ₄ and LiF and heated. The current was increased and heated until the raw material mixture melted. The temperature rising speed at this time was set to 800 ° C. or more within 10 minutes.

  The inside of the tube can be monitored through a mirror, and after visually confirming that the raw material mixture is in a molten state, argon gas is blown into the platinum tube at a pressure of 150 kPa, and the melt is injected into the platinum tube. Extruded down through a small hole. A copper roll rotating at a rotation speed of 500 rpm was provided under the platinum tube, and the melt was brought into contact with the roll and cooled to obtain an active material containing the material of the present invention.

The appearance of the material thus obtained is shown in FIG. FIG. 1 is a photograph of the active material of the present invention, and the unit of the scale in FIG. 1 is mm. As shown in FIG. 1, the cooled active material was a thick, light brown thin plate.
This active material was well ground and subjected to structural analysis by X-ray diffraction. RINT2500 manufactured by Rigaku Corporation was used as the analysis device. The measurement results are shown in FIG. In FIG. 2, a plurality of crystalline peaks were observed, and it was confirmed from these plurality of crystalline peaks that main peaks attributed to LiFePO ₄ and Li ₂ FePO ₄ F were mainly present. In FIG. 2, the vertical axis represents intensity (arbitrary), and the horizontal axis represents diffraction angle 2θ (°).

Example 2
An active material of the present invention was produced in the same manner as in Example 1 except that the rotation speed of the copper roll was changed to 3000 rpm. Increasing the rotational speed increased the cooling rate of the melt.
The appearance of the active material thus obtained is shown in FIG. FIG. 3 is a photograph of the active material of the present invention, and the unit of the scale in FIG. 3 is mm. The cooled active material was thinner and needle-like than in the case of Example 1.

The structural analysis of this active material was performed by X-ray diffraction in the same manner as in Example 1. The measurement results are shown in FIG. From FIG. 4, a plurality of crystalline peaks and a halo pattern considered to be amorphous (or a collection of microcrystals) were recognized. Since the portion of the halo pattern is quite large, the active material in this case is considered to have a low degree of crystallinity and many portions in an amorphous state. Further, from FIG. 4, a plurality of crystalline peaks were observed, and it was confirmed that the main peaks attributed to LiFePO ₄ and Li ₂ FePO ₄ F existed in the plurality of crystalline peaks. Moreover, it was confirmed that the main peak attributed to LiFePO ₄ and Li ₂ FePO ₄ F mainly exists in the crystalline peak.

Example 3
This was the same as in the examples except that Li ₂ O, FeO, P ₂ O ₅ and LiF were used as raw materials, and these were mixed sufficiently in a molar ratio of 1: 2: 1: 2 to use the raw material mixture. An active material of the invention was prepared.
The active material thus obtained has the same shape as in FIG. 3, and as a result of X-ray diffraction measurement, a plurality of crystalline peaks similar to those in FIG. 4 are recognized. It was confirmed that a main peak attributed to ₄ and Li ₂ FePO ₄ F was present.

Example 4
In this example, the raw material mixture was melted using an apparatus different from those in Examples 1 to 3. The same raw material mixture as in Example 1 was placed in a platinum boat and placed in a tubular furnace. Flange was provided on both sides of the tubular furnace so that the atmosphere inside the tube could be controlled. A platinum tube containing the raw material mixture was set and sealed with a flange, and then the pressure was reduced once. Thereafter, high purity argon gas (5N) was introduced into the tube, and the argon gas was continuously flowed after reaching atmospheric pressure. In this state, the temperature of the electric furnace was increased and increased to 900 ° C. at a temperature increase rate of 1000 ° C./h (that is, the temperature was increased to 900 ° C. in 54 minutes).

Hold at 900 ° C. for 3 hours, then cool to 700 ° C. at a rate of 2 ° C./h, cool to 500 ° C. at a rate of 5 ° C./h, cool to 200 ° C. at a rate of 10 ° C./h, The active material of the present invention was produced.
This active material was subjected to X-ray diffraction measurement in the same manner as in Example 1. As a result, a plurality of crystalline peaks similar to those in FIG. 4 were observed, and it was confirmed that a main peak attributed to LiFePO ₄ and Li ₂ FePO ₄ F was present from the plurality of crystalline peaks.

Example 5
LiMnPO ₄ and LiF were used as raw materials. LiMnPO ₄ can be produced using a known technique. Here, it synthesize | combined with the following method.
Lithium carbonate, manganese carbonate, and ammonium dihydrogen phosphate were mixed at a predetermined ratio, and the mixture was calcined in the air at 300 ° C. for 12 hours. The obtained calcined product was pulverized and mixed again, and then calcined in air at 600 ° C. for 48 hours to obtain a powder. As a result of X-ray diffraction measurement, it was confirmed that the obtained powder was LiMnPO ₄ having an olivine structure.

The LiMnPO ₄ powder and LiF powder were mixed well at a molar ratio of 1: 1 to obtain a raw material mixture. This raw material mixture was heated and melted and cooled in the same manner as in Example 2 using the high frequency induction heating method of the coil to obtain the active material of the present invention.
When the appearance of the obtained active material was examined, it was needle-like and transparent white as in Example 2.

Further, this active material was ground well, and the result of structural analysis by X-ray diffraction as in Example 1 is shown in FIG. In FIG. 5, only the halo pattern considered to be almost attributed to amorphous (or a collection of microcrystals) was observed.
In this example, even if the cooling method was the same as in Example 1, it was confirmed that the amorphous state of the active material obtained would change if the Me of LiMePO ₄ was different.

Example 6
LiCoPO ₄ and LiF were used as raw materials. LiCoPO ₄ can be produced using known techniques. Here, it synthesize | combined with the following method.
Lithium carbonate, cobalt oxalate dihydrate, and ammonium dihydrogen phosphate were mixed at a predetermined ratio, and the mixture was calcined in air at 300 ° C. for 12 hours.
The obtained calcined product was pulverized and mixed again, and then calcined in air at 600 ° C. for 48 hours to obtain a powder. As a result of X-ray diffraction measurement, it was confirmed that the obtained powder was LiCoPO ₄ having an olivine structure.

Next, this LiCoPO ₄ powder and LiF powder were mixed well at a molar ratio of 1: 1 to obtain a raw material mixture. This raw material mixture was heated and melted and cooled in the same manner as in Example 2 using the high frequency induction heating method of the coil to obtain the active material of the present invention.
When the appearance of the obtained active material was examined, it was needle-like and had a transparent blue color as in Example 2.

  Further, this active material was ground well, and the result of structural analysis by X-ray diffraction as in Example 1 is shown in FIG. In FIG. 6, a halo pattern considered to be attributed to crystalline and amorphous (or a collection of microcrystals) is recognized, and the active material in this case has a low crystallinity and an amorphous state. It is thought that there are many parts.

Example 7
LiNiPO ₄ and LiF were used as raw materials. LiNiPO ₄ can be produced using known techniques. Here, it synthesize | combined with the following method.
Lithium carbonate, nickel oxide, and ammonium dihydrogen phosphate were mixed at a predetermined ratio, and the mixture was calcined in air at 500 ° C. for 12 hours.
The obtained calcined product was pulverized and mixed again, and then calcined in air at 800 ° C. for 48 hours to obtain a powder. As a result of X-ray diffraction measurement, it was confirmed that the obtained powder was LiNiPO ₄ having an olivine structure.

Next, this LiNiPO ₄ powder and LiF powder were mixed well at a molar ratio of 1: 1 to obtain a raw material mixture. This raw material mixture was heated and melted and cooled in the same manner as in Example 2 using the high frequency induction heating method of the coil to obtain the active material of the present invention.
When the appearance of the obtained active material was examined, it was needle-like and transparent yellow as in Example 2.

Further, this active material was ground thoroughly, and structural analysis was performed by X-ray diffraction in the same manner as in Example 1. As a result, as in FIG. 5 in Example 5, the material was almost amorphous (or a collection of microcrystals). Only halo patterns that were considered to be attributed were observed.
From the above Examples 1 to 7, it is considered that once the raw material mixture was melted, the raw material mixture became homogeneous, side reactions were less likely to occur than in the conventional method, and Li ₂ MePO ₄ F was quickly synthesized. It is done. It has been found that such a method allows easier and simpler synthesis of an active material containing Li ₂ MePO ₄ F.

《Comparative example》
LiFePO ₄ powder synthesized in the same manner as in Example 1 and LiF were mixed well at a molar ratio of 1: 1, and placed in a platinum tube whose outside was covered with a quartz tube. The tip of this quartz tube was sealed and evacuated. The quartz tube was put in an electric furnace, and the temperature was increased to 700 ° C. at a rate of 200 ° C./h, and the temperature was maintained at 700 ° C. for 24 hours. This temperature has not yet reached the melting points of LiFePO ₄ and LiF and was in a solid state. Then, the powdery comparative active material was obtained by cooling.

[Evaluation test]
Next, non-aqueous electrolyte secondary batteries (batteries 1 to 7 and comparative batteries) were produced using the active materials of the present invention produced in Examples 1 to 7 and comparative active materials produced in comparative examples, respectively. The battery was evaluated.
Here, a coin-type lithium secondary battery having the structure shown in FIG. 7 was produced by a conventional method. FIG. 7 shows a schematic longitudinal sectional view of a coin-type lithium secondary battery produced in an example of the present invention. The coin-type lithium secondary battery shown in FIG. 7 includes a positive electrode case 1, a negative electrode case 2, a gasket 3, a positive electrode plate 4, a negative electrode plate 5, and a separator 6.

The positive electrode plate 4 was produced as follows. That is, 80 parts by weight of the above material was mixed with 15 parts by weight of acetylene black as a conductive agent and 5 parts by weight of polytetrafluoroethylene (PTFE) powder as a binder, and well kneaded dry using an agate mortar. The obtained kneaded material was rolled with a rolling roller to obtain a sheet having a thickness of about 0.15 mm. This sheet was punched to a diameter of 10 mm to obtain a positive electrode plate 4.
As the negative electrode plate 5, a metal lithium foil having a thickness of 0.3 mm punched out to a diameter of 17 mm was used.

In addition, in the non-aqueous electrolyte solution, lithium hexafluorophosphate (LiPF ₆ ) as a solute was mixed with 1 in a mixed non-aqueous solvent obtained by mixing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3. A nonaqueous electrolyte obtained by dissolution so as to be 2 mol / L was used.
As the separator 6, a separator having a two-layer structure of a polyethylene layer and a polypropylene layer was used.

The batteries 1 to 7 thus produced and the comparative battery were charged and discharged as follows. First, the battery was charged at a constant current of 0.157 mA (current density of 0.2 mA / cm ² ) until the voltage reached 5.2V. Thereafter, the battery was discharged with the same current until the voltage reached 2.5V. Such charge and discharge were repeated three times as one cycle.
Moreover, about the batteries 1-5 using the material of Examples 1-5, after performing the said charging / discharging, it charges to 5.2V with the electric current of 0.157mA, and discharge is 0.785mA (1mA / cm). ^The battery was discharged to 2.5 V with the current of ² ).

  The discharge capacity per unit weight of active material (mAh / g) up to 2.5 V in the third cycle of the batteries 1 to 7 and the comparative battery is the discharge capacity per unit active material weight in the third cycle (mAh) in Example 1. The ratio (%) when divided by / g) is shown in Table 1.

From the results shown in Table 1, it was found that the discharge capacity was larger than that of the comparative example by any of the manufacturing methods of Examples 1-4. This is considered to be related to the fact that a uniform reaction occurs because the raw material mixture is melted.
Also, include or active material containing Li ₂ MnPO ₄ F as in Example 5, an active material containing Li ₂ CoPO ₄ F as in Example 6, the Li ₂ NiPO ₄ F as in Example 7 It was confirmed that the charge / discharge reaction occurred in the active material. Li ₂ NiPO ₄ F has a low capacity, but this is not due to the manufacturing method, but originally due to the nature of the material itself because the capacity is very small. In addition, it is considered that the discharge capacity can be further increased by devising a method for producing the electrode plate.

Next, the discharge capacity was compared when the discharge current was 0.2 mA / cm ² and when the discharge current was 1 mA / cm ² . In the batteries 1 to 4, the discharge capacity when discharged at 1 mA / cm ² was divided by the discharge capacity when discharged at 0.2 mA / cm ² , and the value was defined as high rate discharge characteristics. Table 2 shows the results of the batteries 1 to 4 at this time.

From the results shown in Table 2, it was found that the battery 2 exhibits high efficiency discharge characteristics. This is presumably because, in the case of the battery 2, the presence ratio of the amorphous or microcrystalline aggregate is large, and the primary particle diameter is very fine, so that the high rate discharge characteristics are excellent.
From the above, it was found that when a battery was produced using an active material produced using the production method of the present invention, a battery having higher capacity or higher rate discharge characteristics was obtained.

  In the above embodiment, a coin-type battery is used, but the present invention is not limited to this. In addition, as a shape of the electrode plate group, the positive electrode plate and the negative electrode plate are also wound in a spiral shape via a separator serving as an insulating layer, and the positive electrode plate via the separator serving as an insulating layer, A similar effect can be obtained with a group of electrode plates in which the negative electrode plate is stacked in a stack. The shape of the exterior body is not limited to the coin case of the above embodiment, for example, in the shape of a cylindrical shape, a square shape and a sheet shape using a laminate sheet sandwiched between aluminum metal foils with a polyolefin resin as the exterior body, Similar effects can be obtained.

According to the present invention, it is possible to synthesize a material containing Li ₂ MePO ₄ F by a manufacturing method that is superior in mass productivity and less likely to cause side reactions. Further, when a battery is produced using the material obtained by the production method of the present invention as an active material, a battery having a high capacity and excellent in high rate discharge can be obtained. Such a high-capacity battery is useful as a driving power source for electronic devices such as notebook computers, mobile phones, and digital still cameras. In the production method of the present invention, a battery having a higher capacity can be realized by appropriately changing the synthesis conditions and the like.

2 is a photograph showing the appearance of the active material of the present invention synthesized in Example 1. FIG. 3 is an XRD chart of the active material of the present invention synthesized in Example 2. FIG. 4 is a photograph showing the appearance of the active material of the present invention synthesized in Example 3. FIG. 6 is an XRD chart of the active material of the present invention synthesized in Example 4. FIG. 6 is an XRD chart of the active material of the present invention synthesized in Example 5. FIG. 6 is an XRD chart of the active material of the present invention synthesized in Example 6. FIG. It is a schematic sectional drawing which shows the structure of the coin-type lithium secondary battery produced in the evaluation test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Positive electrode case 2 ... Negative electrode case 3 ... Gasket 4 ... Positive electrode plate 5 ... Negative electrode plate 6 ... Separator

Claims (1)

A mixture obtained by mixing raw materials of a material represented by the formula: Li ₂ MePO ₄ F (wherein Me is at least one transition metal element selected from the group consisting of Fe, Co, Mn and Ni) the by melting by heating at 1000 ° C. / h or more, to obtain an active material for a non-aqueous electrolyte containing a material expressed by the above formula,
A method for producing an active material for a non-aqueous electrolyte battery.